Glasses



United States Patent() GLASSES Henry H. Blau, Bexley, Ohio, assignor to The Ohio State University Research Foundation, Columbus, Ohio, a corporation of Ohio Original application November 14, 1950, Serial No. 195,691, now Patent No. 2,691,599, dated October 12, 1954. Divided and this application May 10, 1954, Serial No. 428,588

Claims. (Cl. 106-47) This application is a division of my copending application Serial No. 195,691, filed November 14, 1950, which issued as Patent No. 2,691,599, Oct. 12, 1954.

The invention disclosed in this application relates to new glasses which are especially useful for transmission of rays of relatively long wave lengths. Prior hereto glasses have usually been formed of fused silica or fused mixtures of silica with various other components. Alkalies, alkaline earths, borates and similar materials are usually added to glass batches. I have found that certain glasses can be made that are entirely found that certain glasses can be made that are entirely free of silica and of such other materials. Some suggestion has been made that glasses should be formed of pure germania. I have discovered that by mixing germania and lead oxide, fusing the componcnt'sto a liquid mixture and allowing the mixture to solidify, I obtain a glass which has qualities of allowing the transmission of rays of relatively long wave lengths in many respects superior to any other glasses of which I know and which has higher refractive indices than most known glasses. The addition of certain other substances in many instances, is also an aid either in securing better transmission or in securing stability and resistance to chemical attack, and also in improving the viscosity of the glasses. I have found that pure germania glass does not have as good properties in respect to transmission as the glasses which I disclose herein and I have found that it is unstable when exposed to the atmosphere. Germania glasses unfortunately have a much greater tendency to devitrify than do silicate glasses. I have also shown by experiment that pure germania glasses are not as satisfactory in the above and other respects as the glasses formed of the several components which I have disclosed herein.

One of the objects of my invention, therefore, is the production of new glasses.

A further object of my invention is the production of glasses having unusual optical properties such as relatively high indexes of refraction, relatively low dispersion, and relatively high opacity to X-rays and other low wave length radiations.

A further object of my invention is to produce glasses free from or low in alkalies to which colors can nevertheless be imparted.

A further object of my invention is the production of glasses having better qualities with regard to transmission of rays of relatively long wave length, stability, resistance to chemical and atmospheric attack, etc., than previous glasses of which I am aware.y

A further object of my invention is the provision of glasses which allow better transmission of much of the infra red rays.

A further object of my invention is the provision of glasses, having relatively great transmission of infra red rays, which are relatively stable to atmospheric conditions, to abrasion and to chemical attack.

Further objects and features of my invention will be apparent from the subjoined specification and claims when considered in connection with the accompanying drawings illustrating certain embodiments of my invention.

ln the drawings:

Fig. 1 is a diagram showing the limits of the usable glass-forming field of a system of glasses formed by lead oxide, germania and lanthana;

Fig. 2 is a similar diagram showing the limits of the glass-forming field of a glass system in which glasses are formed of lead oxide, germania and alumina; and

Fig. 3 is a similar diagram showing the limits of the glass of the usable glass-forming field of a glass system in which the glasses are formed of the compounds of lead oxide, germania and zirconia.

Referring to the drawings, I show the glasses formed from the components lead oxide, germania and lanthana and having percentages of the components which may be plotted to lie within the areas A, B and C, are usable. Glasses formed of percentages of compounds plotted to lie within the area A are stable and have good transmission of long wave rays. Glasses formed of components having percentages plotted to lie within the area B are stable glasses but the transmission of long wave rays is below the average of the transmission of the glasses formed from percentages of components lying within the area A. Glasses formed of percentages of components plotted to lie within the area C are subject to atmospheric attack but the transmission of fresh glasses formed from percentages of the components shown is fairly good. In my attempts to form glasses having percentages of components lying within the area D, I found such glasses unsatisfactory inasmuch as they were faulty due to the devitriication or incomplete fusion.

Similarly, I found that glasses formed of the components germania, lead oxide and alumina lying within the areas A, B, C and D of Fig. 2 have substantially the same characteristics as the corresponding glasses formed from germania, lead oxide and lanthana which are described above in connection with Fig. l. In the same way glasses formed of lead oxide, germania and zirconia lying within the areas A, B, C and D of Fig. 3 correspond substantially to the corresponding glasses described above in connection with Fig. 1. As shown below, I have also discovered the advantages of a PbO-GeOz-AlzOs-La203 system. I have also discovered the possibilities of using oxides of Various other metals as a third component of a lead oxide-germania glass. Thus, the oxides of the following metals may be used: lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, zinc, gallium, rubidlum, strontium, yettrium, columbium, cadmium, indrum, tin, antimony, cesium, barium, cerium, praseodymiurn, neodymium, samarium, europium, gadolinium, terblum, dysprosium, holmium, erbium, thulium, ytterbium, lutecium, thallium, bismuth and polonium.

Where it is desired to transmit rays of long wave lengths, silicon, boron, and phosphorus, even in small amounts should not be tolerated as the presence of these materials decreases the wave length transmitted. Lanthana, alumina, zirconia, etc., aiect the physical properties of the glass but do not affect the transmission, except as the transmission is affected by being able to increase the ratio of lead oxide to germanium dioxide. The third components mentioned (other than silicon, boron, and phosphorus) affect mainly the working properties of the glass such as viscosity points, handling propertles, etc.

In general the ratio corresponding to the most favorable third constituent (other than GeO and PbO) seems to determine the limit for glass formation. Thus the addition of a minor quantity of MnO to a lead-germanialanthana composition seems to permit the glass to be formed substantially as if the MnO were an additional molecular quantity of LazOa. The addition of lithia to an alumina glass likewise permits the glass formation to fall within the alumina ratio. If anything, these additions extend the limits of the glass-forming elds and increase the usable ratios slightly. I believe that MnO is especially beneficial in this respect.

The limits of the glass-forming field of a system employing the components lead oxide and germania only as established by the weight ratio lead oxide, germania, and lanthana as established by the weight ratio PbO Ge02 are to 2.6 (i. e. from 100% GC02 to 72% PbO Geog with La203 added in amounts from 0 to 13% (naturally addition of La203 decreases the total percentages of PbO and Ge02). The eiect of increasing the ratios of lead oxide as shown above is to increase the total energy transmitted by transmitting longer wave lengths. However, when the maximum ratio is surpassed, the glass tends to devitrify in batches larger than five grams. With good melting techniques, the indications are that the ratio might be extended slightly. The amount of La2O3 which may be added is seen to reach a maximum of 13% at a ratio of about 1.0 and then decreases to about 2% at a ratio of 2.6. Greater additions of La203 caused devitrication. There are indications that small additions of alkalies may aid in increasing the ratio and consequently the total energy transmitted. However, limited quantities of alkalies appear to have little, if any, effect on the transmission by themselves. In all systems studied, relatively high ratios of PbO tend to increase transmission at longer Wave lengths and also reduce the cost of the glass where an expensive network former is involved.

The limits of the glass-forming eld of a mixture of the components lead oxide, germania, and alumina, as established by the weight ratio PbO GB02 are 0 to 4.65 (i. e. from 100% Ge02 to about En, Pbo

Geog

with A1203 added in amounts from 0 to about 11.5%. The eiect of raising the ratio of the added components is the same as in the system PbO-GeOz-LazOa. The amount of A1203 which may be added is seen to reach a maximum at a ratio of about 1.0 (i. e.

57;, Pbo

and then decrease to 4% at a ratio of about 4.6). However, a few more per cent A1203 may be incorporated by using higher melting temperatures. Greater addltions of A1203 than the maximum make fusion more dicult at low ratios, and A1203 in excess of the maximum,

tends to cause devitrication at higher ratios. The main useful purpose of A1203 is to permit glass formation at a higher PbO GB02 ratio. A darkening of the yellow color of the high PbO glasses towards a brown may be observed as A1203 is added and replaces Ge02. The effect of limited quantities of alkalies is the same as in the system PbO-GeOz-Lazos The limits of the glass-forming field of a system consisting of PbO-GeO2-Zr02 as established by the weight ratio PbO Geog are about 0 to 4.4 (i. e. from 100% GeOz to about 79% PbO Geog with ZrO2 added in amounts from 0 to 3%). Larger amounts of ZrO2 cause either incomplete fusion or devitritcation, depending on the ratio of in a system where there is no third component is about 2.13% at a rat1o of The limits of the glass-forming eld of a system consisting of PbO-GeOz-AlzOs--LazOs as established by the weight ratio PbO are about 0 to 4.45 with the sum of the percentages of A1203 and La203 varying from 0 to 10%. In general, the percentage of A1203 should either equal or exceed the percentage of La203 (especially at the higher PbO ratios) to prevent devitrification. The effect of A1203 in this system appears to be identical with that of A1203 in the system Pb0-GeO2-A12O3.

Below the above is set out in table form:

Limits of the glass-forming field in various systems as established by the ratio PbO GC02 Eiect of surpassing This Limit Limiting Etect of Increasing Limits of Etects of Third Com- System Ratios Ratio Above Maximum Third Component ponent At Low Ratios At High Ratios bO-Ge() 1,3203 0 to 2.6 Causes devitricationin 0 to 13%,. Causes devitri- Causes devitri- Very little effect, if any. P zbatches larger than 5 g. cation. fication. Possible decolorization. More resistance to abrasion and chemical s b (I ot 11 57 I dini d Pattaiik' in 1 Pb0. Ge0 A1203 0 to 4.65 ame as a ove mo o-.- nereases o erm s incrcas g rat o. 2 proved melting techculty ofusion. More resistance to nique may extend raio abrasion and chemical to 5.00). attack. pho- GeOz-Zroz 0 to 4.4.-.. Same as above (Im- 0 t0 3% .do do Same as in A1203 system proved melting techwth a possible impairnique may extend mcnt of transmission. ratio slightly). More resistance to abrasion and chemical attack. pb0 .Ge0 A120,-Lmo3 0 to 4.45 Same as above Ccmvoied 0 ----.do -do Same asinAlzOa system.

The process of obtaining these glasses is also important. Water must be removed from the glass. The process of eliminating water absorption bands is quite important and critical. The glass must be melted in a container free from silica and other harmful substances and the melt may be carried on in an atmosphere free from moisture. We prefer however, to dry after melting las disclosed below.

As stated above it is possible to eliminate the water by carrying on the melt in an atmosphere free from moisture. It is more practical however to melt without strict precautions as to moisture and to dry subsequently. We usually move the glass after melting and while in a melted condition to a drying furnace which has an atmosphere free of moisture. Through this furnace we pass a continuous stream of dry gas (such as, for example, nitrogen or oxygen) under a slight positive pressure. We may on the other hand allow the glass to solidify after being melted in an ordinary furnace. We may then remelt to purify of moisture in a drying furnace. In eithcr event the drying furnace eliminates the contamination of water. In order to prevent such contamination, I melt the glass or preferably dry it after melting and possibly after allowing it to harden and remelting in a gas tight furnace chamber through which a continuous stream of dry gas (such as, for example, nitrogen or oxygen) is passed under a slight positive pressure. Thereby the transmission characteristics are so improved that a chart of percent of transmission to wave lengths shows a curve with a higher percentage of transmission throughout and a curve which is smooth and free of dips at varying wave lengths.

Following are examples of glasses formed according to my invention in all of which percentages mentioned are by weight:

Example I I melted together 65.4% PbO, 30.0% GeOz, 4.0% LazOa, 0.6% MnOz. These components were fused and allowed to solidify. Glass was obtained which had good transmission quality in the infra red region, and the manganese dioxide acts to prevent or reduce transmission of visible wave lengths as well as to stabilize the glass in the same way that the lanthana does.

Example Il I melted together 70% lead oxide, 29% germania and 1% lanthana. Glass was obtained which transmitted about 60% of the rays, at a Wave length of 5 microns and approximately of the rays at a wave length of 6 microns.

Example III I melted together and fused a mixture of 68.0% lead oxide, 29.0% germania, 3.0% lanthana and allowed the melt to solidify to form a glass which had similar transmission characteristics.

Example l V I melted together a glass which had a composition of 58.7% lead oxide, 36.6% germania, 4.2% lanthana and 0.5% LizO. The glass had similar good transmission characteristics. The addition of the small amounts of lithia used showed little effect on the infra red transmission; however, its presence reduced the index of refraction to some extent, thus reducing reflexion losses slightly.

Example V I melted together 78.0% PbO, 18.0% GeOz, 4.0% A1203. These components were fused and allowed to solidify. Glass was obtained which had about 35.0% transmission at 6 microns.

Example VI I melted together 75.0% lead oxide, 20.0% germania and 2% lanthana and 3% alumina. Glass was obtained which transmitted about of the rays, at a wave length of 6 microns.

Example VII I melted together and fused a mixture of 70.0% lead oxide, 29.0% germania, 1% zirconia and allowed the melt to solidify to form a glass which transmitted about 25% of the rays at a wave length of 6 microns.

Example VIII I melted together a glass which had a composition of 77.0% lead oxide, 18.0% germania, 4% alumina, and 1% zirconia. The glass transmitted about 30% of the rays at 6 microns.

It is to be understood that the above described embodiments of my invention are for the purpose of illustration only and various changes may be made therein without departing from the spirit and scope of my invention.

I claim:

1. A glass consisting by weight of a trace to 79% lead oxide, from 18% to 99.9% germania and from a trace to 3% zirconia.

2. A glass consisting of a plurality of oxides of which lead oxide and germanium oxide comprise by weight at least 97% of the glass and of which the remainder consists of zirconia and in which glass consists by weight of from a trace to 79% lead oxide and 18% to 99.9% germania and from a trace to 3% of Zirconia.

3. A glass consisting by weight of a trace to 79% lead oxide, from 18% to 99.9% germania and from a trace to 3% zirconia, in which the ratio of lead oxide to germania does not exceed the ratio of 4.4 to 1.

4. A glass consisting of lead oxide, germania and zirconia in which the glass consists by weight of from 20 to 79% lead oxide, from 18 to 80% germania and from a trace to 3% zirconia.

5. A glass consisting of lead oxide, germania, and zirconia in which the glass consists by weight of from 60 to 79% lead oxide, from 18 to 40% germania, and from a trace to 3% zirconia.

6. A method of making a glass consisting of lead oxide, germania, and a stabilizing component consisting of zirconia which method consists of melting together the components of which lead oxide and germania comprise by weight at least 97% of the mixture and of which germania comprises by weight at least 18% of the mixture and thereafter removing the melt to and maintaining it in an atmosphere free of water and water vapor, while the glass is in a heated condition and during the cooling process.

7. A method of making glass consisting of lead oxide, germania, and a stabilizing component consisting of zirconia which method consists of melting together components which are silica free of which lead oxide and germania comprise by weight at least 97% of the mixture, and of which germania comprises by weight at least 18% of the mixture in a container free from silica and thereafter maintaining the glass in an atmosphere free of water, while the glass is in a heated condition and during the cooling process.

8. A method of making a glass consisting of lead oxide, germania, and a stabilizing component consisting of zirconia which method consists of melting together components which are silica free of which lead oxide and germania comprise by weight at least 97% of the mixture, and of which germania comprises by weight at least 18% of the mixture in a container free from silica.

9. A method of making a glass consisting of lead oxide, germania, and a stabilizing component consisting of zirconia which method consists of melting together the components of which lead oxide and germania comprise by weight at least 97% of the mixture and of which germania comprises by weight at least 18% of the mixture, removing the melt to and maintaining it until cooled in a gas tight furnace and in an atmosphere free of water and water vapor, and passing through the furnace a continuous stream of dry gas under a slight positive pressure.

l0. A method of making a glass consisting of lead oxide, germania, and a stabilizing component consisting of zirconia which method consists of melting together the components of which lead oxide and germania comprise by weight at least 97% of the mixture and of which germania comprises by weight at least 18% of the mixture to form a glass, and removing the glass, and remelting the glass and maintaining it until cooled in a gas tight furnace and in an atmosphere free of water and water vapor.

References Cited in the file of this patent UNITED STATES PATENTS 2,330,324 Adams Sept. 28, 1943 2,386,685 Hood Oct. 9, 1945 2,663,658 Schurecht Dec. 22, 1953 

1. A GLASS CONSISTING BY WEIGHT OF A TRACE TO 79% LEAD OXIDE, FROM 18% TO 99.9% GERMANIA AND FROM A TRACE TO 3% ZIRCONIA.
 6. A METHOD OF MAKING A GLASS CONSISTING OF LEAD OXIDE, GERMANIA, AND A STABILIZING COMPONENT CONSISTING OF ZIRCONIA WHICH METHOD CONSISTS OF MELTING TOGETHER THE COMPONENTS OF WHICH LEAD OXIDE AND GERMANIA COMPRISE BY WEIGHT AT LEAST 97% OF THE MIXTURE AND OF WHICH GERMANIA COMPRISES BY WEIGHT AT LEAST 18% OF THE MIXTURE AND THEREAFTER REMOVING THE MELT TO AND MAINTAINING IT IN AN ATMOSPHERE FREE OF WATER AND WATER VAPOR, WHILE THE GLASS IS IN A HEATED CONDITION AND DURING THE COOLING PROCESS. 